Add option to keep evidence when suspending accounts

Fix #547

When selected, before the account's data is removed, some of it
is denormalized into a separate, symmetrically-encrypted table. In
particular:

- The e-mail
- All IPs used to access the account
- SHA256 fingerprints of all uploaded files
- URIs of accounts followed by or following the account
- URIs of accounts that were invited

app/controllers/api/v1/admin/account_actions_controller.rb

@@ -26,7 +26,8 @@ class Api::V1::Admin::AccountActionsController < Api::BaseController
       :report_id,
       :warning_preset_id,
       :text,
-      :send_email_notification
+      :send_email_notification,
+      :create_account_summary
     )
   end
 end